Kilogram-Scale Fabrication of a Robust Olefin-Linked Covalent Organic Framework for Separating Ethylene from a Ternary C₂ Hydrocarbon Mixture

Abstract

One-step adsorptive purification of ethylene (C 2 H 4 ) from a ternary mixture of acetylene (C 2 H 2 ), C 2 H 4, and ethane (C 2 H 6 ) by a single material is of great importance but challenging in the petrochemical industry. Herein, a chemically robust olefin-linked covalent organic framework (COF), NKCOF-62, is designed and synthesized by a melt polymerization method employing tetramethylpyrazine and terephthalaldehyde as cheap monomers. This method avoids most of the disadvantages of classical solvothermal methods, which enable the cost-effective kilogram fabrication of olefin-linked COFs in one pot. Furthermore, NKCOF-62 shows remarkably selective adsorption of C 2 H 2 and C 2 H 6 over C 2 H 4 thanks to its unique pore environments and suitable pore size. Breakthrough experiments demonstrate that polymer-grade C 2 H 4 can be directly obtained from C 2 H 2 /C 2 H 6 /C 2 H 4 (1/1/1) ternary mixtures through a single separation process. Notably, NKCOF-62 is the first demonstration of the potential to use COFs for C 2 H 2 /C 2 H 6 /C 2 H 4 separation, which provides a blueprint for the design and construction of robust COFs for industrial gas separations.